System And Method For Manipulating An Anatomy

ABSTRACT

Surgical systems and methods for manipulating an anatomy with a tool include defining a first virtual boundary associated with the anatomy and a second virtual boundary associated with the anatomy. The first virtual boundary is activated in a first mode. Movement of the tool is constrained in relation to the first virtual boundary in the first mode. The first virtual boundary is deactivated in a second mode. Movement of the tool is constrained in relation to the second virtual boundary in the second mode.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to and the benefit of United Statesprovisional patent application No. 62/163,672, filed May 19, 2015, thedisclosure of which is hereby incorporated by reference in its entirety.

TECHNICAL FIELD

The present invention relates generally to a system and method formanipulating an anatomy with a tool of a surgical system, and morespecifically, constraining the tool using virtual boundaries.

BACKGROUND

Recently, operators have found it useful to use robotic devices toassist in the performance of surgical procedures. A robotic devicetypically includes a moveable arm having a free, distal end, which maybe placed with a high degree of accuracy. A tool that is applied to thesurgical site attaches to the free end of the arm. The operator is ableto move the arm and thereby precisely position the tool at the surgicalsite to perform the procedure.

In robotic surgery, virtual boundaries are created prior to surgeryusing computer aided design software to delineate areas in which thetool may maneuver from areas in which the tool is restricted. Forinstance, in orthopedic surgery a virtual cutting boundary may becreated to delineate sections of bone to be removed by the tool duringthe surgery from sections of bone that are to remain after the surgery.

A navigation system tracks movement of the tool to determine a positionand/or orientation of the tool relative to the virtual boundary′. Therobotic system cooperates with the navigation system to guide movementof the tool so that the tool does not move beyond the virtual boundary.Virtual boundaries are often created in a model of a patient's bone andfixed with respect to the bone so that when the model is loaded into thenavigation system, the navigation system may track movement of thevirtual boundary by tracking movement of the bone.

Operators often desire dynamic control of the tool in different cuttingmodes during a surgical operation. For example, in some instances, theoperator may desire a manual mode to control the tool manually for bulkcutting of the anatomy. In other instances, the operator may desire tocontrol the tool in an autonomous mode for automated and highly accuratecutting of the anatomy. In conventional systems, a virtual boundaryassociated with a target surface of the anatomy remains activeregardless of the mode of control. In other words, the same virtualboundary is on whether the tool is controlled in the autonomous mode ormanual mode, for example. The manipulator generally does not allowadvancement of the tool beyond the boundary in either mode. However, insome cases, the manipulator may inadvertently allow movement of the toolbeyond the boundary. For instance, in the manual mode, the operator mayapply such a large amount of force on the tool that exceeds the abilityof the manipulator to prevent movement of the tool beyond the boundary.In this case, cutting of the anatomy may occur beyond the virtualboundary thereby deviating from the desired target surface.

There is a need in the art for systems and methods for solving at leastthe aforementioned problems.

SUMMARY

One embodiment of a system for manipulating an anatomy is provided. Thesystem includes a manipulator having abase and a linkage. A tool iscoupled to the manipulator and movable relative to the base to interactwith the anatomy. A controller is configured to generate a first virtualboundary associated with the anatomy and a second virtual boundaryassociated with the anatomy. The controller is configured to controlmovement of the tool in a first mode and a second mode. The controlleractivates the first virtual boundary in the first mode to constrain thetool in relation to the first virtual boundary. The controllerdeactivates the first virtual boundary in the second mode to constrainthe tool in relation to the second virtual boundary.

One embodiment of a method of operating a surgical system formanipulating an anatomy with a tool is provided. The method includesdefining a first virtual boundary associated with the anatomy and asecond virtual boundary associated with the anatomy. The first virtualboundary is activated in a first mode. Movement of the tool isconstrained in relation to the first virtual boundary in the first mode.The first virtual boundary is deactivated in a second mode. Movement ofthe tool is constrained in relation to the second virtual boundary inthe second mode.

The system and method advantageously provide the opportunity toselectively control activation of the intermediate virtual boundarybetween the first and second modes. By doing so, the system and methodprovide a different virtual boundary configuration for each of the firstand second modes thereby increasing versatility and performance of thesurgical system.

BRIEF DESCRIPTION OF THE DRAWINGS

Advantages of the present invention will be readily appreciated as thesame becomes better understood by reference to the following detaileddescription when considered in connection with the accompanying drawingswherein:

FIG. 1 is a perspective view of a system for manipulating an anatomy ofa patient with a tool according to one embodiment of the invention.

FIG. 2 is a schematic view of a controller for controlling the surgicalsystem according to one embodiment of the invention.

FIG. 3 illustrates the tool interacting with the anatomy along a toolpath to form a target surface according to one embodiment of theinvention.

FIG. 4 illustrates operation of the system in a first mode wherein thetool in constrained in relation to an intermediate virtual boundaryspaced with respect to a target virtual boundary.

FIG. 5 illustrates operation of the system in a second mode wherein thetool in constrained in relation to the target virtual boundary that isoffset from a target surface of the anatomy.

FIG. 6 illustrates operation of the system in the first mode wherein thetool in constrained in relation to the intermediate virtual boundary andwherein the target virtual boundary remains activated.

FIG. 7 illustrates operation of the system in the second mode whereinthe tool in constrained in relation to the target virtual boundaryaligned with the target surface of the anatomy.

FIG. 8 illustrates operation of the system in the first mode wherein thetool in constrained in relation to the intermediate virtual boundary andwherein the target virtual boundary is deactivated.

FIG. 9 illustrates operation of the system in the first mode wherein thetool in constrained in relation to the intermediate virtual boundaryhaving a profile different than the target virtual boundary.

FIG. 10 illustrates operation of the system in the second mode whereinthe tool in constrained in relation to the target virtual boundary′having a profile different than the target surface.

FIG. 11 illustrates operation of the system in the first mode whereinthe tool is constrained between the intermediate and target virtualboundaries.

FIG. 12 illustrates operation of the system in the first mode whereinthe tool is constrained between the intermediate virtual boundary andthe target surface.

FIGS. 13A-13C illustrate characteristics of the anatomy resulting afterbulk cutting in the first mode, according to one example.

FIGS. 14A-14C illustrate characteristics of the anatomy resulting afterfine cutting in the second mode, according to one example.

FIG. 15 illustrates operation of the system using three virtualboundaries each activated in a separate mode.

FIG. 16 illustrates operation of the system using more than one tool andthree virtual boundaries that are simultaneously activated.

DETAILED DESCRIPTION I. Overview

Referring to the Figures, wherein like numerals indicate like orcorresponding parts throughout the several views, a system 10 and methodfor manipulating an anatomy of a patient 12 are shown throughout. Asshown in FIG. 1, the system 10 is a robotic surgical cutting system forcutting away material from the anatomy of the patient 12, such as boneor soft tissue. In FIG. 1, the patient 12 is undergoing a surgicalprocedure. The anatomy in FIG. 1 includes a femur (F) and a tibia (T) ofthe patient 12. The surgical procedure may involve tissue removal. Inother embodiments, the surgical procedure involves partial or total kneeor hip replacement surgery. The system 10 is designed to cut awaymaterial to be replaced by surgical implants such as hip and kneeimplants, including unicompartmental, bicompartmental, or total kneeimplants. Some of these types of implants are shown in U.S. patentapplication Ser. No. 13/530,927, entitled, “Prosthetic Implant andMethod of Implantation,” the disclosure of which is hereby incorporatedby reference. Those skilled in the art appreciate that the system andmethod disclosed herein may be used to perform other procedures,surgical or non-surgical, or may be used in industrial applications orother applications where robotic systems are utilized.

The system 10 includes a manipulator 14. The manipulator 14 has a base16 and a linkage 18. The linkage 18 may comprise links forming a serialarm or parallel arm configuration. A tool 20 couples to the manipulator14 and is movable relative to the base 16 to interact with the anatomy.The tool 20 forms part of an end effector 22 attached to the manipulator14. The tool 20 is grasped by the operator. One exemplary arrangement ofthe manipulator 14 and the tool 20 is described in U.S. Pat. No.9,119,655, entitled, “Surgical Manipulator Capable of Controlling aSurgical Instrument in Multiple Modes,” the disclosure of which ishereby incorporated by reference. The manipulator 14 and the tool 20 maybe arranged in alternative configurations. The tool 20 can be like thatshown in U.S. Patent Application Publication No. 2014/0276949, filed onMar. 15, 2014, entitled, “End Effector of a Surgical RoboticManipulator,” hereby incorporated by reference. The tool 20 includes anenergy applicator 24 designed to contact the tissue of the patient 12 atthe surgical site. The energy applicator 24 may be a drill, a saw blade,a bur, an ultrasonic vibrating tip, or the like. The manipulator 14 alsohouses a manipulator computer 26, or other type of control unit.

Referring to FIG. 2, the system 10 includes a controller 30. Thecontroller 30 includes software and/or hardware for controlling themanipulator 14. The controller 30 directs the motion of the manipulator14 and controls an orientation of the tool 20 with respect to acoordinate system. In one embodiment, the coordinate system is amanipulator coordinate system MNPL (see FIG. 1). The manipulatorcoordinate system MNPL has an origin, and the origin is located at apoint on the manipulator 14. One example of the manipulator coordinatesystem MNPL is described in U.S. Pat. No. 9,119,655, entitled, “SurgicalManipulator Capable of Controlling a Surgical Instrument in MultipleModes,” the disclosure of which is hereby incorporated by reference.

The system 10 further includes a navigation system 32. One example ofthe navigation system 32 is described in U.S. Pat. No. 9,008,757, filedon Sep. 24, 2013, entitled, “Navigation System Including Optical andNon-Optical Sensors,” hereby incorporated by reference. The navigationsystem 32 is set up to track movement of various objects. Such objectsinclude, for example, the tool 20, and the anatomy, e.g., femur F andtibia T. The navigation system 32 tracks these objects to gatherposition information of each object in a localizer coordinate systemLCLZ. Coordinates in the localizer coordinate system LCLZ may betransformed to the manipulator coordinate system MNPL using conventionaltransformation techniques. The navigation system 32 is also capable ofdisplaying a virtual representation of their relative positions andorientations to the operator.

The navigation system 32 includes a computer cart assembly 34 thathouses a navigation computer 36, and/or other types of control units. Anavigation interface is in operative communication with the navigationcomputer 36. The navigation interface includes one or more displays 38.First and second input devices 40, 42 such as a keyboard and mouse maybe used to input information into the navigation computer 36 orotherwise select/control certain aspects of the navigation computer 36.Other input devices 40, 42 are contemplated including a touch screen(not shown) or voice-activation. The controller 30 may be implemented onany suitable device or devices in the system 10, including, but notlimited to, the manipulator computer 26, the navigation computer 36, andany combination thereof.

The navigation system 32 also includes a localizer 44 that communicateswith the navigation computer 36. In one embodiment, the localizer 44 isan optical localizer and includes a camera unit 46. The camera unit 46has an outer casing 48 that houses one or more optical position sensors50. The system 10 includes one or more trackers. The trackers mayinclude a pointer tracker PT, a tool tracker 52, a first patient tracker54, and a second patient tracker 56. The trackers include active markers58. The active markers 58 may be light emitting diodes or LEDs. In otherembodiments, the trackers 52, 54, 56 may have passive markers, such asreflectors, which reflect light emitted from the camera unit 46. Thoseskilled in the art appreciate that the other suitable tracking systemsand methods not specifically described herein may be utilized.

In the illustrated embodiment of FIG. 1, the first patient tracker 54 isfirmly affixed to the femur F of the patient 12 and the second patienttracker 56 is firmly affixed to the tibia T of the patient 12. Thepatient trackers 54, 56 are firmly affixed to sections of bone. The tooltracker 52 is firmly attached to the tool 20. It should be appreciatedthat the trackers 52, 54, 56 may be fixed to their respective componentsin any suitable manner.

The trackers 52, 54, 56 communicate with the camera unit 46 to provideposition data to the camera unit 46. The camera unit 46 provides theposition data of the trackers 52, 54, 56 to the navigation computer 36.In one embodiment, the navigation computer 36 determines andcommunicates position data of the femur F and tibia T and position dataof the tool 20 to the manipulator computer 26. Position data for thefemur F, tibia T, and tool 20 may be determined by the tracker positiondata using conventional registration/navigation techniques. The positiondata includes position information corresponding to the position and/ororientation of the femur F, tibia T, tool 20 and any other objects beingtracked. The position data described herein may be position data,orientation data, or a combination of position data and orientationdata.

The manipulator computer 26 transforms the position data from thelocalizer coordinate system LCLZ into the manipulator coordinate systemMNPL by determining a transformation matrix using the navigation-baseddata for the tool 20 and encoder-based position data for the tool 20.Encoders (not shown) located at joints of the manipulator 14 are used todetermine the encoder-based position data. The manipulator computer 26uses the encoders to calculate an encoder-based position and orientationof the tool 20 in the manipulator coordinate system MNPL. Since theposition and orientation of the tool 20 are also known in the localizercoordinate system LCLZ, the transformation matrix may be generated.

As shown in FIG. 2, the controller 30 further includes software modules.The software modules may be part of a computer program or programs thatoperate on the manipulator computer 26, navigation computer 36, or acombination thereof, to process data to assist with control of thesystem 10. The software modules include sets of instructions stored inmemory on the manipulator computer 26, navigation computer 36, or acombination thereof, to be executed by one or more processors of thecomputers 26, 36. Additionally, software modules for prompting and/orcommunicating with the operator may form part of the program or programsand may include instructions stored in memory on the manipulatorcomputer 26, navigation computer 36, or a combination thereof. Theoperator interacts with the first and second input devices 40, 42 andthe one or more displays 38 to communicate with the software modules.

In one embodiment, the controller 30 includes a manipulator controller60 for processing data to direct motion of the manipulator 14. Themanipulator controller 60 may receive and process data from a singlesource or multiple sources.

The controller 30 further includes a navigation controller 62 forcommunicating the position data relating to the femur F, tibia T, andtool 20 to the manipulator controller 60. The manipulator controller 60receives and processes the position data provided by the navigationcontroller 62 to direct movement of the manipulator 14. In oneembodiment, as shown in FIG. 1, the navigation controller 62 isimplemented on the navigation computer 36.

The manipulator controller 60 or navigation controller 62 may alsocommunicate positions of the patient 12 and tool 20 to the operator bydisplaying an image of the femur F and/or tibia T and the tool 20 on thedisplay 38. The manipulator computer 26 or navigation computer 36 mayalso display instructions or request information on the display 38 suchthat the operator may interact with the manipulator computer 26 fordirecting the manipulator 14.

As shown in FIG. 2, the controller 30 includes a boundary generator 66.The boundary generator 66 is a software module that may be implementedon the manipulator controller 60, as shown in FIG. 2. Alternatively′,the boundary generator 66 may be implemented on other components, suchas the navigation controller 62. As described in detail below, theboundary generator 66 generates the virtual boundaries for constrainingthe tool 20.

A tool path generator 68 is another software module run by thecontroller 30, and more specifically, the manipulator controller 60. Thetool path generator 68 generates a tool path 70 as shown in FIG. 3,which represents a bone, a section of which is to be removed to receivean implant. In FIG. 3, the tool path 70 is represented by the back andforth line. The smoothness and quality of the finished surface dependsin part of the relative positioning of the back and forth line. Morespecifically, the closer together each back and forth pass of the line,the more precise and smooth is the finished surface. Dashed line 84represents the perimeter of the bone that is to be removed usingmanipulator 14. One exemplary system and method for generating the toolpath 70 is explained in U.S. Pat. No. 9,119,655, entitled, “SurgicalManipulator Capable of Controlling a Surgical Instrument in MultipleModes,” the disclosure of which is hereby incorporated by reference.

II. System and Method Overview

The system 10 and method for manipulating the anatomy with the tool 20include defining with the controller 30, a first, or intermediatevirtual boundary 90 and a second, or target virtual boundary 80associated with the anatomy, as shown in FIGS. 4 and 5. The intermediatevirtual boundary 90 is spaced apart from the target virtual boundary 80.The intermediate virtual boundary 90 is activated in a first mode asshown in FIG. 4. Movement of the tool 20 is constrained in relation tothe intermediate virtual boundary 90 in the first mode. The intermediatevirtual boundary 90 is deactivated in a second mode, as shown in FIG. 5.Movement of the tool 20 is constrained in relation to the target virtualboundary 80 in the second mode.

One exemplary system and method for generating the virtual boundaries80, 90 is explained in U.S. Pat. No. 9,119,655, entitled, “SurgicalManipulator Capable of Controlling a Surgical Instrument in MultipleModes,” the disclosure of which is hereby incorporated by reference. Theboundary generator 66 generates maps that define the target andintermediate virtual boundaries 80, 90. These boundaries 80, 90delineate between tissue the tool 20 should remove and tissue the tool20 should not remove. Alternatively, these boundaries 80, 90 delineatebetween tissue to which the tool 20 energy applicator 24 should beapplied and tissue to which the energy applicator 24 should not beapplied. As such, the target and intermediate virtual boundaries 80, 90are cutting or manipulation boundaries, which limit movement of the tool20. Often, but not always, the virtual boundaries 80, 90 are definedwithin the patient 12.

As shown throughout, the target and intermediate virtual boundaries 80,90 independently constrain movement of the tool 20 between the first andsecond modes. That is, the tool 20 is constrained by either theintermediate virtual boundary 90 in the first mode or the target virtualboundary 80 in the second mode. Methods for constraining movement of thetool 20 are explained in U.S. Pat. No. 9,119,655, entitled, “SurgicalManipulator Capable of Controlling a Surgical Instrument in MultipleModes,” the disclosure of which is hereby incorporated by reference.

The surgical system 10 allows switching between the first and secondmodes to provide different constraint configurations for the tool 20.When the first mode is switched to the second mode, as shown in FIG. 5the intermediate virtual boundary 90 is deactivated, leaving the targetvirtual boundary 80. Thus, in the second mode, the tool 20 is permittedto reach the target virtual boundary 80 because the intermediate virtualboundary 90 is not constraining the tool 20. The tool 20 is constrainedin relation to the target virtual boundary 80 when the intermediatevirtual boundary 90 is inactivated.

When the second mode is switched to the first mode, as shown in FIG. 4,the intermediate virtual boundary 90 is activated or re-activated. Thetool 20 is constrained in relation to the intermediate virtual boundary90 when the intermediate virtual boundary 90 is activated. Thus, in thefirst mode, the intermediate virtual boundary 90 prevents the tool 20from reaching the target virtual boundary 80.

The manipulator 14 is configured to receive instructions from thecontroller 30 and move the tool 20 in relation to the intermediatevirtual boundary 90 in the first mode and/or the target virtual boundary80 in the second mode. The navigation system 32 tracks movement of thetool 20 in relation to the intermediate virtual boundary 90 in the firstmode and/or the target virtual boundary 80 in the second mode. As thetool 20 moves, the manipulator 14 and navigation system 32 cooperate todetermine if the tool 20 is inside the intermediate virtual boundary 90in the first mode and/or the target virtual boundary 80 in the secondmode. The manipulator 14 selectively limits the extent to which the tool20 moves. Specifically, the controller 30 constrains the manipulator 14from movement that would otherwise result in the application of the tool20 outside of the intermediate virtual boundary 90 in the first modeand/or the target virtual boundary 80 in the second mode. If theoperator applies forces and torques that would result in the advancementof the tool 20 beyond the intermediate virtual boundary 90 in the firstmode and/or target virtual boundary 80 in the second mode, themanipulator 14 does not emulate this intended positioning of the tool20.

As shown in FIG. 5, the target virtual boundary 80 is associated withthe anatomy, and more specifically a target surface 92 of the anatomy.The target virtual boundary 80 is defined in relation to the targetsurface 92. Target surface 92 is also the outline of the bone remainingafter the removal procedure and is the surface to which the implant isto be mounted. In other words, the target surface 92 is a contiguousdefined surface area of the tissue that is to remain after cutting hascompleted.

As shown in FIG. 5, during the procedure, the target virtual boundary 80may be slightly offset or spaced apart from the target surface 92. Inone embodiment, this is done to account for the size and manipulationcharacteristics of the tool 20. The manipulation characteristics of thetool 20 may cause the tool 20 to breach the target virtual boundary 80.To account for this overreaching, the target virtual boundary 80 may betranslated from target surfaces 82 by a predetermined distance definedbetween the target surface 92 and the target virtual boundary 80. In oneexample, the distance is equivalent to half of the thickness of the tool20. In another embodiment, the target virtual boundary 80 may beslightly offset or spaced apart from the target surface 92 depending onhow the tool 20 and energy applicator 24 are tracked. For example, theenergy applicator 24 may be tracked based on points based on a center ofthe energy applicator 24 rather than points based on an exterior cuttingsurface of the energy applicator 24. In such instances, offsetting thetarget virtual boundary 80 from the target surface 92 providesaccommodates the center tracking to prevent overshooting of the targetsurface 92. For instance, when the energy applicator of the tool 20 is aspherical bur, the target virtual boundary is offset by half thediameter of the bur when the tool center point (TCP) of the bur is beingtracked. As a result, when the TCP is on the target virtual boundary 80,the outer surface of the bur is at the target surface 92.

The intermediate virtual boundary 90 is spaced apart from the targetvirtual boundary 80. As shown in FIG. 4, the intermediate virtualboundary 90 is spaced further from the target surface 92 than the targetvirtual boundary 80 is spaced from the target surface 92. In essence,the target virtual boundary 80 is located between the target surface 92and the intermediate virtual boundary 90. Since the intermediate virtualboundary 90 is spaced further from the target surface 92, movement ofthe tool 20 is generally more restricted in relation to the intermediatevirtual boundary 90 as compared in relation to the target virtualboundary 80. Said differently, movement of the tool 20 is morerestricted in the first mode as compared with the second mode.

A zone 100 is defined between the target and intermediate virtualboundaries 80, 90, as shown in FIG. 4. The boundaries 80, 90 may bespaced according to any suitable distance. In one example, the targetand intermediate virtual boundaries 80, 90 are spaced by approximatelyone half millimeter such that the zone 100 has a thickness of one halfmillimeter. In one sense, the intermediate virtual boundary 90 may beconsidered an offset boundary in relation to the target virtual boundary80. In general, the controller 30 prevents the tool 20 from penetratingthe zone 100 in the first mode. Preventing the tool 20 from penetratingthe zone 100 in the first mode may occur regardless of whether or notthe target virtual boundary 80 is active. The controller 30 allows thetool 20 to penetrate the zone 100 in the second mode. The zone 100 maybe defined independent of whether the target and/or intermediate virtualboundaries 80, 90 are active or inactive.

The target and intermediate virtual boundaries 80, 90 may have the sameprofile has shown in FIG. 4. Specifically, the target and intermediatevirtual boundaries 80, 90 have profiles that are similar to the targetsurface 92. Having similar profiles may be useful to promote gradualformation of the target surface 92.

Displays 38 may show representations of the target and intermediatevirtual boundaries 80, 90 and the anatomy being treated. Additionally,information relating to the target and intermediate virtual boundaries80, 90 may be forwarded to the manipulator controller 60 to guide themanipulator 14 and corresponding movement of the tool 20 relative tothese virtual boundaries 80, 90 so that the tool 20 does not intrude onsuch.

The manipulator controller 60 may continuously track movement of thetarget and intermediate virtual boundaries 80, 90. In some instances,the anatomy may move from a first position to a second position duringthe procedure. In such instances, the manipulator controller 60 updatesthe position of the virtual boundaries 80, 90 consistent with the secondposition of the anatomy.

In one embodiment, the first mode and/or second mode is/are anautonomous mode or a manual mode. Examples of the autonomous mode andmanual mode are described in U.S. Pat. No. 9,119,655, entitled,“Surgical Manipulator Capable of Controlling a Surgical Instrument inMultiple Modes,” the disclosure of which is hereby incorporated byreference.

In one embodiment, in the first mode, the system 10 operates in themanual mode. The operator manually directs, and the manipulator 14controls, movement of the tool 20 and, in turn, the energy applicator 24at the surgical site. The operator physically contacts the tool 20 tocause movement of the tool 20. The manipulator 14 monitors the forcesand torques placed on the tool 20 by the operator in order to positionthe tool 20. These forces and torques are measured by a sensor that ispart of the manipulator 14. In response to the applied forces andtorques, the manipulator 14 mechanically moves the tool 20 in a mannerthat emulates the movement that would have occurred based on the forcesand torques applied by the operator. Movement of the tool 20 in thefirst mode is constrained in relation to the intermediate virtualboundary 90. In this case, the intermediate virtual boundary 90 acts asa haptic boundary and the manipulator 14 provides the operator withhaptic feedback to indicate the location of the intermediate virtualboundary 90 to the operator. For instance, by virtue of the manipulator14 preventing or resisting movement of the tool 20 beyond theintermediate virtual boundary 90, the operator haptically senses avirtual wall when reaching the intermediate virtual boundary 90.

At any time during manual manipulation in the first mode, or aftermanipulation in the first mode is complete, the system 10 allowsswitching from the first mode to the second mode. In one embodiment,switching between the first and second modes occurs in response tomanual input. For example, the operator may use some form of control tomanage remotely which of the first and second modes should be active.Alternatively, switching may be implemented autonomously in response tocertain events or conditions. For example, the system 10 may determinethat the requisite amount of tissue has been removed in the first modeand switch to the second mode in response. Those skilled in the artappreciate that switching between first and second modes may beperformed according to other methods not explicitly described herein.

In the second mode, in one embodiment, the manipulator 14 directsautonomous movement of the tool 20 and, in turn, the energy applicator24 at the surgical site. The manipulator 14 is capable of moving thetool 20 free of operator assistance. Free of operator assistance maymean that an operator does not physically contact the tool 20 to applyforce to move the tool 20. Instead, the operator may use some form ofcontrol to remotely manage starting and stopping of movement. Forexample, the operator may hold down a button of a remote control tostart movement of the tool 20 and release the button to stop movement ofthe tool 20. Alternatively, the operator may press a button to startmovement of the tool 20 and press a button to stop movement of the tool20. Movement of the tool 20 in the second mode is constrained inrelation to the target virtual boundary 80.

The system 10 and method advantageously provide the opportunity toselectively control activation of the intermediate virtual boundary 90between the first and second modes. By doing so, the system 10 andmethod provide different virtual boundary configurations for each of thefirst and second modes. This increases versatility of the surgicalsystem and performance of the operator. In some embodiments, thisadvantageously provides the opportunity for the operator to use themanipulator 14 in a bulk-manipulation fashion in the first mode. Theoperator may initially operate the tool 20 manually in order to remove alarge mass of tissue. This part of the procedure is sometimes referredto as debulking. The operator, knowing that the intermediate virtualboundary 90 is constraining the tool 20 away from the target surface 92,may take measures to perform bulk-manipulation that is much faster thanotherwise possible during autonomous manipulation. Once the bulk of thetissue is removed manually, the system 10 may be switched to the secondmode to provide autonomous manipulation of the remaining portion of thetissue in a highly accurate and controlled manner. Said differently, inthe second mode, the operator may require fine positioning of theinstrument to define the surfaces of the remaining tissue. This part ofthe procedure is sometimes known as the finishing cut, and is possiblebecause the intermediate virtual boundary 90 is inactive and the targetvirtual boundary 80 is active.

III. Other Embodiments

The target and virtual boundaries 80, 90 may be derived from variousinputs to the manipulator 14, and more specifically, the boundarygenerator 66. One input into the boundary generator 66 includespreoperative images of the site on which the procedure is to beperformed. If the manipulator 14 selectively removes tissue so thepatient 12 may be fitted with an implant, a second input into theboundary generator 66 is a map of the shape of the implant. The initialversion of this map may come from an implant database. The shape of theimplant defines the boundaries of the tissue that should be removed toreceive the implant. This relationship is especially true if the implantis an orthopedic implant intended to be fitted to the bone of thepatient 12.

Another input into boundary generator 66 is the operator settings. Thesesettings may indicate to which tissue the energy applicator 24 should beapplied. If the energy applicator 24 removes tissues, the settings mayidentify the boundaries between the tissue to be removed and the tissuethat remains after application of the energy applicator 24. If themanipulator 14 assists in the fitting of an orthopedic implant, thesesettings may define where over the tissue the implant should bepositioned. These settings may be entered preoperatively using a dataprocessing unit. Alternatively, these settings may be entered through aninput/output unit associated with one of the components of the system 10such as with navigation interface 40, 42.

Based on the above input data and instructions, boundary generator 66may generate the target and intermediate virtual boundaries 80, 90. Theboundaries 80, 90 may be two-dimensional or three-dimensional. Forexample, the target and intermediate virtual boundaries 80, 90 may begenerated as a virtual map or other three-dimensional model, as shown inthe Figures. The created maps or models guide movement of the tool 20.The models may be displayed on displays 38 to show the locations of theobjects. Additionally, information relating to the models may beforwarded to the manipulator controller 60 to guide the manipulator 14and corresponding movement of the tool 20 relative to the target andintermediate virtual boundaries 80, 90.

In practice, prior to the start of the procedure the operator at thesurgical site may set an initial version of the virtual target andintermediate virtual boundaries 80, 90. At the start of the procedure,data that more precisely defines the implant that is to be actuallyfitted to the patient 12 may be loaded into the boundary generator 66.Such data may come from a storage device associated with the implantsuch as a memory stick or an RFID tag. Such data may be a component ofthe implant database data supplied to the boundary generator 66. Thesedata are based on post manufacture measurements of the specific implant.These data provide a definition of the shape of the specific implantthat, due to manufacturing variations, may be slightly different thanthe previously available stock definition of implant shape. Based onthis implant-specific data, the boundary generator 66 may update thetarget and intermediate virtual boundaries 80, 90 to reflect theboundaries between the tissue to be removed and the tissue that shouldremain in place. Implants that could be implanted into the patient 12include those shown in U.S. patent application Ser. No. 13/530,927,filed on Jun. 22, 2012 and entitled, “Prosthetic Implant and Method ofImplantation”, hereby incorporated by reference. The implants disclosedherein could be implanted in the patient 12 after the appropriate amountof material, such as bone, is removed. Other implants are alsocontemplated.

In one embodiment, the target virtual boundary 80 is derived from pointsin a coordinate system associated with the anatomy. The target virtualboundary 80 may be interpolated by connecting each of the capturedpoints together. This creates a web or mesh that defines the targetvirtual boundary 80. If only two points are captured, the target virtualboundary 80 may be a line between the points. If three points arecaptured, the target virtual boundary 80 may be formed by linesconnecting adjacent points. The displays 38 may provide visual feedbackof the shape of the target virtual boundary 80 created. The inputdevices 40, 42 may be utilized to control and modify the target virtualboundary 80 such as by shifting the boundary, enlarging or shrinking theboundary, changing the shape of the target virtual boundary 80, etc.Those skilled in the art understand that the target virtual boundary 80may be created according to other methods not specifically describedherein.

Alternative arrangements and configurations of the target virtualboundary 80 are shown in FIGS. 7 and 10. In some instances, as shown inFIG. 7, it may be suitable to align the target virtual boundary 80directly with the target surface 92 of the anatomy rather than to havean offset between the two. For example, the manipulation characteristicsof the tool 20 may not extend beyond the target virtual boundary 80.Additionally or alternatively, the tool 20 may be tracked based onpoints that are on an exterior surface of the energy applicator 24rather than points that are in the center of the energy applicator 24.In such instances, aligning the target virtual boundary 80 with thetarget surface 92 provides accurate manipulation to create the targetsurface 92. In yet another embodiment, the tool 20 may be tracked basedon an envelope outlining a range of movement of the exterior surface ofthe tool 20. For instance, when the tool 20 is a saw blade, the envelopeencompasses the range of movement of the exterior surface of the sawblade such that movement of the exterior surface of the saw blade duringoscillations of the saw blade is captured within the envelope.Positioning of the target virtual boundary 80 may take into account theenvelope.

In other examples, as shown in FIG. 5, the target virtual boundary 80 isgenerally un-aligned with the target surface 92. Instead, the targetvirtual boundary 80 is spaced apart from and rests beyond the targetsurface 92. Those skilled in the art appreciate that the target virtualboundary 80 may have other configurations not specifically recitedherein.

The intermediate virtual boundary 90 may be formed in a similar manneras the target virtual boundary 80. Alternatively, the controller 30 mayderive the intermediate virtual boundary 90 from the target virtualboundary 80. For example, the controller 30 may copy the target virtualboundary 80 to form the intermediate virtual boundary 90. The copy ofthe target virtual boundary 80 may be modified or transformed accordingto any suitable method to form the intermediate virtual boundary 90. Forexample, the copy of the target virtual boundary 80 may be translated,shifted, skewed, resized, rotated, reflected, and the like. Thoseskilled in the art understand that the intermediate virtual boundary 90may be derived from the target virtual boundary 80 according to othermethods not specifically described herein.

The target virtual boundary 80 and the intermediate virtual boundary 90may have any suitable profile. For example, as shown in FIG. 5, thetarget virtual boundary 80 has a profile that is similar to the profileof the target surface 92. In FIG. 10, the target virtual boundary 80 hasa profile that is planar or flat. In FIG. 4, the intermediate virtualboundary 90 has a profile that is similar to the profile of the targetsurface 92. In FIG. 9, the intermediate virtual boundary 90 has aprofile that is planar or flat. Those skilled in the art appreciate thatthe target virtual boundary 80 and the intermediate virtual boundary 90may have other profiles not specifically recited herein.

The target and intermediate virtual boundaries 80, 90 need not have thesame profile, as shown in FIG. 4. Instead, the boundaries 80, 90 mayhave the different profiles with respect to one another, as shown inFIG. 9. In FIG. 9, the profile of the target virtual boundary 80 issimilar to the profile of the target surface 92 whereas the profile ofthe intermediate virtual boundary 90 is planar. Of course, those skilledin the art appreciate that either profile of the boundaries 80, 90 maydiffer from those illustrated in FIG. 9. The profiles of each of theboundaries 80, 90 may be generated manually or automatically inaccordance with any suitable technique. Having different profiles may beuseful depending on several factors, including, but not limited to, thetool 20 and/or mode being used.

Several different embodiments are possible for the target virtualboundary 80 in view of the first mode. As described, in the first mode,the intermediate virtual boundary 90 is active and the tool 20 isconstrained in relation to the intermediate virtual boundary 90.However, activation and deactivation of the target virtual boundary 80may be controlled in the first mode. For example, as shown in FIGS. 4,6, and 9, the target virtual boundary 80 may be activated in the firstmode simultaneously while the intermediate boundary 90 is active. In oneexample, this may be done for redundancy purposes. As described, theintermediate boundary 90 is an important feature of the system 10because it operates as a cutting boundary. Any errors in implementationof the intermediate boundary 90 may, in turn, leave the target surface92 exposed to error. By simultaneously activating the target virtualboundary 80, the system 10 increases reliability by having the targetvirtual boundary 80 as a back up to the intermediate virtual boundary90. This may also allow the manipulator 14 to operate at higher speedsknowing that the target virtual boundary 80 is provided as a redundancy.Alternatively, as shown in FIG. 8, the target virtual boundary 80 may bedeactivated in the first mode. This may be done to preserve computingresources, reduce complexity in implementation, and the like.

Control of the target virtual boundary 80 in the first mode may beautomatic or manual. For example, the operator may manually activate ordeactivate the target virtual boundary 80 in the first mode.Alternatively, the system 10 may automatically determine whether it isappropriate to activate the target virtual boundary 80 depending oncertain events or conditions. For example, detection of instability ofthe system 10 may trigger automatic activation of the target virtualboundary 80 in the first mode.

The first mode and the second mode may be different type (i.e.,manual/autonomous) or the same type depending on the application and avariety of other factors. One such factor is duration of the operatingprocedure, which is largely affected by a feed rate of the tool 20. Thefeed rate is the velocity at which a distal end of the energy applicator24 advances along a path segment. In general, in the autonomous mode,the manipulator 14 may be more accurate but provides a slower feed ratethan in the manual mode. In the manual mode, the manipulator 14 may beless accurate but is capable of providing a faster feed rate than in theautonomous mode. This trade-off between accuracy and feed rate is onefactor dictating what type of control is implemented during the firstand second modes.

A frequency of back-and-forth oscillations of the tool 20 along thecutting path 70 may differ between the first and second modes.Generally, the greater the frequency of the oscillations, the closertogether the cutting path 70 oscillations and the “finer” the cutprovided by the tool 20. On the other hand, the lesser the frequency ofthe oscillations, the more spaced apart the cutting path 70 oscillationsand the “bulkier” the cut provided by the tool 20.

Generally, as the tool 20 traverses the cutting path 70, the tool 20forms ribs 110 in the anatomy (distal femur), as shown in FIGS. 13 and14. Examples of such ribs are shown in U.S. patent application Ser. No.14/195,113, entitled, “Bone Pads,” the disclosure of which is herebyincorporated by reference. The specific three-dimensional geometry ofthe ribs 110 is the result of a rotational cutting tool, such as a burrfor example, making a plurality of channeled preparations 112. In theembodiments shown, the plurality of channeled preparations 112 follow asubstantially linear path resulting from back and forth movement of thetool 20 along the cutting path 70. The ribs 110 have a height 114, awidth 116 and a plurality of protrusions 118. When the first and secondmodes exhibit different cutting path 70 oscillation frequencies, thefirst and second modes produce ribs 110 having different configurations.

In one example, the oscillations are more frequent in the second modethan the first mode. For example, FIGS. 13A-C illustrate ribs 110resulting from bulk-cutting in the first mode and FIGS. 14A-C illustrateribs 110 resulting from fine-cutting in the second mode. Consequently,the ribs 110 are formed differently between the first and second modes.Specifically, the ribs 110 formed in the first mode (FIG. 13B) exhibit alarger peak-to-peak distance between adjacent ribs 110 as compared withribs 110 formed in the second mode (FIG. 14B), which are closertogether. The height and/or width of the ribs 110 may also be differentbetween the first and second modes. For example, the width 116 of theribs 110 in the bulk-cutting mode (FIG. 13C) is greater than the width116 of the ribs 110 in the fine-cutting mode (FIG. 14C). Conversely, theheight 114 of the ribs 110 in the bulk-cutting mode (FIG. 13C) is lessthan the height 114 of the ribs 110 in the fine-cutting mode (FIG. 14C).Additionally, the geometry of the protrusions 118 formed in the firstmode may differ from those formed in the second mode. The first andsecond modes advantageously provide different surface finishesappropriate for the specific application. Those skilled in the artrecognize that the first and second modes may cause differences incharacteristics of the anatomy other than those described herein withrespect to the ribs.

In one embodiment, the first mode is the autonomous mode and the secondmode is the manual mode. Movement of the tool 20 occurs autonomously inthe first mode and is constrained in relation to the intermediatevirtual boundary 90. Autonomous manipulation in the first mode isswitched to manual manipulation in the second mode. Movement of the tool20 occurs manually in the second mode and is constrained in relation tothe target virtual boundary 80. Specifically, the operator may rely onthe surgical system 10 to perform a majority of the manipulation of thetissue autonomously in the first mode. As needed, the operator mayswitch to manual manipulation in the second mode to interface directlywith the target virtual boundary 80, which is closer to the targetsurface 92. By doing so, the operator can perform versatile procedures,such as creating irregular surface finishes on the target surface 92.The system 10 and method allow the operator to make final cuts in thetarget surface 92 that secure the implant better than may be plannedwith autonomous manipulation. Moreover, operators may prefer not toallow the system 10 to autonomously cut tissue entirely up to the targetsurface 92. Having the intermediate virtual boundary 90 activated in thefirst mode provides added comfort for operators during autonomousmanipulation because the intermediate virtual boundary 90 is spaced fromthe target virtual boundary 80.

In another embodiment, the first mode and the second mode are bothmanual modes. Movement of the tool 20 occurs manually in the first modeand is constrained in relation to the intermediate virtual boundary 90.Manual manipulation in the first mode is switched to manual manipulationin the second mode. Although manual manipulation is preserved in thesecond mode, the boundary configuration changes because the intermediatevirtual boundary 90 is deactivated. In the second mode, movement of thetool 20 occurs manually and is constrained in relation to the targetvirtual boundary 80. This embodiment advantageously provides theopportunity for the operator to use the manipulator 14 in abulk-manipulation fashion in both the first and second modes. Theoperator, knowing that the intermediate virtual boundary 90 isconstraining the tool 20 away from the target surface 92, may takemeasures to perform bulk manipulation that is much faster and moreaggressive than otherwise possible during autonomous manipulation. Oncethe bulk of the tissue is removed manually in the first mode, the system10 may be switched to the second mode for allowing manual manipulationof the remaining portion of the tissue. In the second mode, the operatormay manually create irregular or fine surface finishes on the targetsurface 92 in relation to the target virtual boundary 80.

In yet embodiment, the first mode and the second mode are bothautonomous modes. Movement of the tool 20 occurs autonomously in thefirst mode and is constrained in relation to the intermediate virtualboundary 90. Autonomous manipulation in the first mode is switched toautonomous manipulation in the second mode. Although switching to thesecond mode maintains autonomous manipulation, the boundaryconfiguration changes by deactivating the intermediate virtual boundary90. In the second mode, movement of the tool 20 occurs autonomously andis constrained in relation to the target virtual boundary 80. Thisembodiment advantageously provides the opportunity to manipulate thetissue autonomously in a highly accurate and controlled mannerthroughout the first and second modes. Additionally, the operator mayexamine the tissue after autonomous manipulation in the first mode. Inother words, rather than having the surgical device 10 autonomouslymanipulate the tissue entirely up to the target surface 92, the firstmode may be used as a first-phase whereby the operator checks theprogress and accuracy of the autonomous cutting before deactivating theintermediate virtual boundary 90 in the second mode.

In one embodiment, the system and method implement “n” modes. Forexample, the system and method may implement three or more modes. Thefirst mode may be a manual mode. The second mode may be an autonomousmode exhibiting autonomous bulk-cutting, as shown in FIG. 13, forexample. The third mode may be an autonomous mode exhibiting autonomousfine-cutting, as shown in FIG. 14, for example. Those skilled in the artappreciate that any of the “n” modes may be a mode other than anautonomous or manual mode described herein.

The system and method may implement “n” virtual boundaries. For example,the system and method may implement three or more virtual boundaries.The “n” virtual boundaries may be implemented for the “n” modes. Oneexample of a three-virtual boundary implementation is illustrated inFIG. 15. In FIG. 15, the first virtual boundary 90, the second virtualboundary 80, and a third virtual boundary 120 are associated with theanatomy. Here, first virtual boundary 90 is provided to promote removalof cartilage and a superficial layer of bone, the second virtualboundary 80 is provided to promote removal of a deeper layer of bone forplacement of an implant, and the third virtual boundary 120 is providedto promote formation of a hole in preparation for insertion of apeg/tail to secure the implant. The first virtual boundary 90 isactivated in the first mode. Movement of the tool is constrained inrelation to the first virtual boundary 90 in the first mode. The firstvirtual boundary 90 is deactivated in the second mode. The third virtualboundary 120 may remain active in the second mode. Movement of the toolis constrained in relation to the second virtual boundary 80 in thesecond mode. The second virtual boundary 80 is deactivated in a thirdmode. Movement of the tool is constrained in relation to the thirdvirtual boundary 120 in the third mode.

In some embodiments, the “n” virtual boundaries are tissue specific.That is, the virtual boundaries are configured to constrain the tool 20in relation to different types of tissue. For example, the “n” virtualboundaries may constrain the tool 20 in relation to soft tissue,cartilage, bone, ligaments, and the like. This may be done to protectthe specific tissue from manipulation by the tool 20.

Additionally or alternatively, the “n” virtual boundaries arearea/location specific. That is, the virtual boundaries are configuredto constrain the tool 20 in relation to different areas or locations.For example, the “n” virtual boundaries may constrain the tool 20 inrelation to other objects at the surgical site, such as retractors,other tools, trackers, and the like. Additionally, any one of the “n”virtual boundaries may serve as an irrigation boundary preventing thetool 20 from accessing a wet location in which the anatomy is undergoingirrigation. Those skilled in the art recognize that the “n” virtualboundaries and “n” modes may be implemented according to various othertechniques not specifically recited herein.

In other embodiments, the “n” virtual boundaries may be used inconjunction with more than one surgical tool 20. For example, as shownin FIG. 16, a first surgical tool 20 a and a second surgical tool 20 bare provided. The tools 20 a, 20 b move in a coordinated and/orsynchronized fashion. The first virtual boundary 90 is defined withrelation to an upper surface of the anatomy and the second and thirdvirtual boundaries 80, 120 are defined along respective right and leftsurfaces of the anatomy. Here, the virtual boundaries 80, 90, 120 may besimultaneously active. Moreover, the virtual boundaries 80, 90, 120 mayintersect, or touch, one another. In other examples, one tool 20 is usedfor manipulation while another tool is used for tissue retraction. Insuch instances, one virtual boundary may function as a manipulationconstraining boundary while another virtual boundary functions as atissue retraction boundary to prevent the retraction tool from leavingthe intended area of retraction.

Any of the “n” virtual boundaries may be defined with respect to theanatomy such that virtual boundaries move as the anatomy positionchanges. This may be accomplished using the navigation and controltechniques described herein.

The “n” virtual boundaries may be defined with respect to the sameanatomy, as shown throughout the Figures, for example. In suchinstances, each of the “n” virtual boundaries follows the anatomy as theanatomy moves. Alternatively, the “n” virtual boundaries may be definedwith respect to the different anatomy. For example, some “n” virtualboundaries may be defined with respect to the femur while other “n”virtual boundaries are defined with respect to the tibia. This may bedone to protect the tibia from inadvertent manipulation. In suchinstances, spacing between the virtual boundaries may vary dependingupon respective movement between the femur and tibia.

The controller 30 detects when the first mode is switched to the secondmode, and vice-versa. The controller 30 may produce an alert to theoperator to inform the operator whether constraint of the tool 20 isoccurring in relation to the target virtual boundary 80 or intermediatevirtual boundary 90. The alert may be visual, haptic, audible, and thelike. Those skilled in the art recognize that the alert may beimplemented according to various other ways not specifically describedherein.

In some instances, the tool 20 may be within the zone 100 in the secondmode at a moment when the system 10 is switched to the first mode. Insuch instances, the tool 20 may become trapped between the intermediatevirtual boundary 90 and the target virtual boundary 80 or target surface92. In one example, as shown in FIG. 11, the target virtual boundary 80remains active in the first mode such that the tool 20 is trappedbetween the intermediate virtual boundary 90 and the target virtualboundary 80. In another example, as shown in FIG. 12, the target virtualboundary 80 is deactivated in the first mode such that the tool 20 istrapped between the intermediate virtual boundary 90 and the targetsurface 92.

Trapping the tool 20 in this manner may be deliberate or unintentional.When unintentional, the controller 30 may evaluate the position of thetool 20 when the second mode is switched to the first mode to preventtrapping the tool 20. For example, if the tool 20 is in the zone 100 atthe time of switching to the first mode, the controller 30 may instructthe manipulator 14 to withdraw the tool 20 from the zone 100 such thatthe tool 20 is pulled beyond the intermediate virtual boundary 90. Thismay entail temporarily deactivating the intermediate virtual boundary 90to allow exit of the tool 20. In other instances, it may be intended totrap the tool 20 within the zone 100 in the first mode. Trapping thetool 20 may be done to use the intermediate virtual boundary 90 as anupper constraining or cutting boundary. To illustrate, in the secondmode, the tool 20 may penetrate tissue in the zone 100 with a narrowincision. Thereafter, the first mode may be re-activated to trap thetool 20 within the zone 100 with the intermediate virtual boundary 90.The operator may then remove tissue in the zone 100 manually orautonomously knowing that the tool 20 is constrained from above. Thisconfiguration may be useful for creating burrows in the tissue, and thelike.

Several embodiments have been discussed in the foregoing description.However, the embodiments discussed herein are not intended to beexhaustive or limit the invention to any particular form. Theterminology which has been used is intended to be in the nature of wordsof description rather than of limitation. Many modifications andvariations are possible in light of the above teachings and theinvention may be practiced otherwise than as specifically described.

The many features and advantages of the invention are apparent from thedetailed specification, and thus, it is intended by the appended claimsto cover all such features and advantages of the invention which fallwithin the true spirit and scope of the invention. Further, sincenumerous modifications and variations will readily occur to thoseskilled in the art, it is not desired to limit the invention to theexact construction and operation illustrated and described, andaccordingly, all suitable modifications and equivalents may be resortedto, falling within the scope of the invention.

1. A surgical system for manipulating an anatomy, said systemcomprising: a manipulator having a base and a linkage; a tool coupled tosaid manipulator and movable relative to said base to interact with theanatomy; and a controller configured to generate a first virtualboundary associated with the anatomy and a second virtual boundaryassociated with the anatomy and control movement of said tool in a firstmode and a second mode and wherein said controller activates said firstvirtual boundary in said first mode to constrain said tool in relationto said first virtual boundary and wherein said controller deactivatessaid first virtual boundary in said second mode to constrain said toolin relation to said second virtual boundary.
 2. The surgical system ofclaim 1 wherein said controller is configured to prevent said tool fromreaching said second virtual boundary in said first mode.
 3. Thesurgical system of claim 1 wherein said controller is configured toallow said tool to reach said second virtual boundary in said secondmode.
 4. The surgical system of claim 1 wherein a zone is definedbetween said first and second virtual boundaries and wherein saidcontroller is configured to prevent said tool from penetrating said zonein said first mode and allow said tool to penetrate said zone in saidsecond mode.
 5. The surgical system of claim 1 wherein said firstvirtual boundary is spaced apart from a target surface of the anatomy.6. The surgical system of claim 1 wherein said first mode is one of anautonomous mode and a manual mode and said second mode is the other oneof said autonomous mode and said manual mode.
 7. The surgical system ofclaim 1 wherein said first and second modes are either both autonomousmodes or both manual modes.
 8. The surgical system of claim 1 wherein afeed rate of said tool is different between said first and second modes.9. The surgical system of claim 1 wherein said controller is configuredto activate said second virtual boundary in said first mode.
 10. Thesurgical system of claim 1 wherein said first virtual boundary isfurther defined as an intermediate virtual boundary and wherein saidsecond virtual boundary is further defined as a target virtual boundary.11. The surgical system of claim 1 wherein said first virtual boundaryis spaced apart from said second virtual boundary.
 12. The surgicalsystem of claim 1 wherein said controller is configured to control saidtool for bulk cutting the anatomy in said first mode and to control saidtool for fine cutting the anatomy in said second mode.
 13. A method ofoperating a surgical system for manipulating an anatomy with a tool, themethod comprising: defining a first virtual boundary associated with theanatomy; defining a second virtual boundary associated with the anatomy;activating the first virtual boundary in a first mode; constrainingmovement of the tool in relation to the first virtual boundary in thefirst mode; deactivating the first virtual boundary in a second mode;and constraining movement of the tool in relation to the second virtualboundary in the second mode.
 14. The method of claim 13 furtherincluding the step of preventing the tool from reaching the secondvirtual boundary in the first mode
 15. The method of claim 13 furtherincluding the step of allowing the tool to reach the second virtualboundary in the second mode.
 16. The method of claim 13 furtherincluding the steps of defining a zone between the first and secondvirtual boundaries and preventing the tool from penetrating the zone inthe first mode and allowing the tool to penetrate the zone in the secondmode.
 17. The method of claim 13 wherein the step of defining the firstvirtual boundary is further defined as spacing the first virtualboundary apart from a target surface of the anatomy.
 18. The method ofclaim 13 wherein the step of constraining movement of the tool in thefirst mode occurs in one of an autonomous mode and a manual mode andwherein the step of constraining movement of the tool in the second modeoccurs in the other one of the autonomous mode and the manual mode. 19.The method of claim 13 wherein the steps of constraining movement of thetool in the first mode and constraining movement of the tool in thesecond mode both occur in either autonomous modes or manual modes. 20.The method of claim 13 further including operating the tool according todifferent feed rates between the first and second modes.
 21. The methodof claim 13 further including the step of manually switching between thefirst and second modes.
 22. The method of claim 13 further including thestep of autonomously switching between the first and second modes. 23.The method of claim 13 further including the step of activating thesecond virtual boundary in the first mode.
 24. The method of claim 13further including bulk cutting the anatomy in the first mode and finecutting the anatomy in the second mode.
 25. The method of claim 13wherein the first virtual boundary is further defined as an intermediatevirtual boundary and wherein the second virtual boundary is furtherdefined as a target virtual boundary.
 26. The method of claim 13 furtherincluding spacing apart the first virtual boundary and the secondvirtual boundary.